Jack,

A few questions to start the brainstorming process:

How large is your board and the spacing between mounting screws?  What
is the board thickness and plating finish?  Any mounting screws in the
middle of the board?  What size/type of hardware?  How is hardware being
installed - larger head driver or screwdriver.  More than one assembler?
Has the board seen any vibration or thermal stress after mounting?  Does
the mounting screw area have top layer clad?  What percentage have
exhibited this failure mode?

100 mils is too close for my liking, but I don't have a good rule of
thumb for you though.

Jim Carlson 
Quality/Configuration Manager 
L-3 Communications 
Applied Signal & Image Technology 
443-457-1111 Ext. 238


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: Monday, January 14, 2013 11:36 AM
To: [log in to unmask]
Subject: [TN] Mounting Hardware to QFP Component Lead

To the assembly professionals out there:

Have you ever had reliability issues with mounting screws if they are
near a Quad Flat-Pack? My 144 pin land pattern is pretty close (100mils)
but we are mounting the board into a very flat structure (no bowing) I
can't imagine the compression of the board material could affect
gull-wing style lead connections (maybe BGA?) but I don't know...

thanks,
Jack


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